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<a class="jxr_linenumber" name="1" href="#1">1</a>   <strong class="jxr_keyword">package</strong> net.big_oh.common.algorithms.winnowing;
<a class="jxr_linenumber" name="2" href="#2">2</a>   
<a class="jxr_linenumber" name="3" href="#3">3</a>   <strong class="jxr_keyword">import</strong> java.math.BigInteger;
<a class="jxr_linenumber" name="4" href="#4">4</a>   <strong class="jxr_keyword">import</strong> java.security.MessageDigest;
<a class="jxr_linenumber" name="5" href="#5">5</a>   <strong class="jxr_keyword">import</strong> java.security.NoSuchAlgorithmException;
<a class="jxr_linenumber" name="6" href="#6">6</a>   <strong class="jxr_keyword">import</strong> java.util.ArrayList;
<a class="jxr_linenumber" name="7" href="#7">7</a>   <strong class="jxr_keyword">import</strong> java.util.Collections;
<a class="jxr_linenumber" name="8" href="#8">8</a>   <strong class="jxr_keyword">import</strong> java.util.HashSet;
<a class="jxr_linenumber" name="9" href="#9">9</a>   <strong class="jxr_keyword">import</strong> java.util.List;
<a class="jxr_linenumber" name="10" href="#10">10</a>  <strong class="jxr_keyword">import</strong> java.util.Set;
<a class="jxr_linenumber" name="11" href="#11">11</a>  
<a class="jxr_linenumber" name="12" href="#12">12</a>  <em class="jxr_comment">/*</em>
<a class="jxr_linenumber" name="13" href="#13">13</a>  <em class="jxr_comment">Copyright (c) 2009 Dave Wingate dba Big-Oh Software (www.big-oh.net)</em>
<a class="jxr_linenumber" name="14" href="#14">14</a>  
<a class="jxr_linenumber" name="15" href="#15">15</a>  <em class="jxr_comment">Permission is hereby granted, free of charge, to any person</em>
<a class="jxr_linenumber" name="16" href="#16">16</a>  <em class="jxr_comment">obtaining a copy of this software and associated documentation</em>
<a class="jxr_linenumber" name="17" href="#17">17</a>  <em class="jxr_comment">files (the "Software"), to deal in the Software without</em>
<a class="jxr_linenumber" name="18" href="#18">18</a>  <em class="jxr_comment">restriction, including without limitation the rights to use,</em>
<a class="jxr_linenumber" name="19" href="#19">19</a>  <em class="jxr_comment">copy, modify, merge, publish, distribute, sublicense, and/or sell</em>
<a class="jxr_linenumber" name="20" href="#20">20</a>  <em class="jxr_comment">copies of the Software, and to permit persons to whom the</em>
<a class="jxr_linenumber" name="21" href="#21">21</a>  <em class="jxr_comment">Software is furnished to do so, subject to the following</em>
<a class="jxr_linenumber" name="22" href="#22">22</a>  <em class="jxr_comment">conditions:</em>
<a class="jxr_linenumber" name="23" href="#23">23</a>  
<a class="jxr_linenumber" name="24" href="#24">24</a>  <em class="jxr_comment">The above copyright notice and this permission notice shall be</em>
<a class="jxr_linenumber" name="25" href="#25">25</a>  <em class="jxr_comment">included in all copies or substantial portions of the Software.</em>
<a class="jxr_linenumber" name="26" href="#26">26</a>  
<a class="jxr_linenumber" name="27" href="#27">27</a>  <em class="jxr_comment">THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,</em>
<a class="jxr_linenumber" name="28" href="#28">28</a>  <em class="jxr_comment">EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES</em>
<a class="jxr_linenumber" name="29" href="#29">29</a>  <em class="jxr_comment">OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND</em>
<a class="jxr_linenumber" name="30" href="#30">30</a>  <em class="jxr_comment">NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT</em>
<a class="jxr_linenumber" name="31" href="#31">31</a>  <em class="jxr_comment">HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,</em>
<a class="jxr_linenumber" name="32" href="#32">32</a>  <em class="jxr_comment">WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING</em>
<a class="jxr_linenumber" name="33" href="#33">33</a>  <em class="jxr_comment">FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR</em>
<a class="jxr_linenumber" name="34" href="#34">34</a>  <em class="jxr_comment">OTHER DEALINGS IN THE SOFTWARE.</em>
<a class="jxr_linenumber" name="35" href="#35">35</a>  <em class="jxr_comment">*/</em>
<a class="jxr_linenumber" name="36" href="#36">36</a>  
<a class="jxr_linenumber" name="37" href="#37">37</a>  <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="38" href="#38">38</a>  <em class="jxr_javadoccomment"> * &lt;p&gt;</em>
<a class="jxr_linenumber" name="39" href="#39">39</a>  <em class="jxr_javadoccomment"> * A Java implementation of winnowing, a document fingerprinting algorithm.</em>
<a class="jxr_linenumber" name="40" href="#40">40</a>  <em class="jxr_javadoccomment"> * Applying the winnowing algorithm to a source document results in the</em>
<a class="jxr_linenumber" name="41" href="#41">41</a>  <em class="jxr_javadoccomment"> * generation of a set of fingerprint values, that can be used to identify</em>
<a class="jxr_linenumber" name="42" href="#42">42</a>  <em class="jxr_javadoccomment"> * partial text duplications in other source documents (that have also been</em>
<a class="jxr_linenumber" name="43" href="#43">43</a>  <em class="jxr_javadoccomment"> * fingerprinted).</em>
<a class="jxr_linenumber" name="44" href="#44">44</a>  <em class="jxr_javadoccomment"> * &lt;/p&gt;</em>
<a class="jxr_linenumber" name="45" href="#45">45</a>  <em class="jxr_javadoccomment"> * &lt;p&gt;</em>
<a class="jxr_linenumber" name="46" href="#46">46</a>  <em class="jxr_javadoccomment"> * Following are important arguments that you can vary to change the manner in</em>
<a class="jxr_linenumber" name="47" href="#47">47</a>  <em class="jxr_javadoccomment"> * which your source documents are fingerprinted:</em>
<a class="jxr_linenumber" name="48" href="#48">48</a>  <em class="jxr_javadoccomment"> * &lt;/p&gt;</em>
<a class="jxr_linenumber" name="49" href="#49">49</a>  <em class="jxr_javadoccomment"> * &lt;ul&gt;</em>
<a class="jxr_linenumber" name="50" href="#50">50</a>  <em class="jxr_javadoccomment"> * &lt;li&gt;</em>
<a class="jxr_linenumber" name="51" href="#51">51</a>  <em class="jxr_javadoccomment"> * k - The size of the k-grams generated by the fingerprinting process. Text</em>
<a class="jxr_linenumber" name="52" href="#52">52</a>  <em class="jxr_javadoccomment"> * duplications shorter than size k will not be discovered. Note that in order</em>
<a class="jxr_linenumber" name="53" href="#53">53</a>  <em class="jxr_javadoccomment"> * to compare the fingerprints for two documents (to detect duplication), both</em>
<a class="jxr_linenumber" name="54" href="#54">54</a>  <em class="jxr_javadoccomment"> * documents must have been ingerprinted using the same value for k.&lt;/li&gt;</em>
<a class="jxr_linenumber" name="55" href="#55">55</a>  <em class="jxr_javadoccomment"> * &lt;li&gt;</em>
<a class="jxr_linenumber" name="56" href="#56">56</a>  <em class="jxr_javadoccomment"> * t - The guarantee threshold. Text duplications of length t or greater are</em>
<a class="jxr_linenumber" name="57" href="#57">57</a>  <em class="jxr_javadoccomment"> * guaranteed to be discoverable.&lt;/li&gt;</em>
<a class="jxr_linenumber" name="58" href="#58">58</a>  <em class="jxr_javadoccomment"> * &lt;/ul&gt;</em>
<a class="jxr_linenumber" name="59" href="#59">59</a>  <em class="jxr_javadoccomment"> * &lt;p&gt;</em>
<a class="jxr_linenumber" name="60" href="#60">60</a>  <em class="jxr_javadoccomment"> * For guidance on setting k &amp; t values, see</em>
<a class="jxr_linenumber" name="61" href="#61">61</a>  <em class="jxr_javadoccomment"> * <a href="http://theory.stanford.edu/~aiken/publications/papers/sigmod03.pdf." target="alexandria_uri">http://theory.stanford.edu/~aiken/publications/papers/sigmod03.pdf.</a></em>
<a class="jxr_linenumber" name="62" href="#62">62</a>  <em class="jxr_javadoccomment"> * &lt;/p&gt;</em>
<a class="jxr_linenumber" name="63" href="#63">63</a>  <em class="jxr_javadoccomment"> * &lt;p&gt;</em>
<a class="jxr_linenumber" name="64" href="#64">64</a>  <em class="jxr_javadoccomment"> * Before fingerprinting documents with the winnowing algorithm it is common to</em>
<a class="jxr_linenumber" name="65" href="#65">65</a>  <em class="jxr_javadoccomment"> * pre-process those documents to remove whitespace and transform structural</em>
<a class="jxr_linenumber" name="66" href="#66">66</a>  <em class="jxr_javadoccomment"> * elements to canonical form. For example, before fingerprinting a SQL</em>
<a class="jxr_linenumber" name="67" href="#67">67</a>  <em class="jxr_javadoccomment"> * statement, one might remove comment lines (because they are "whitespace") as</em>
<a class="jxr_linenumber" name="68" href="#68">68</a>  <em class="jxr_javadoccomment"> * well as rewrite join clauses in alphabetical order. This implementation of</em>
<a class="jxr_linenumber" name="69" href="#69">69</a>  <em class="jxr_javadoccomment"> * winnowing provides the {@link WinnowingWhitespaceFilter} and</em>
<a class="jxr_linenumber" name="70" href="#70">70</a>  <em class="jxr_javadoccomment"> * {@link WinnowingTextTransformer} classes to support whitespace removal and</em>
<a class="jxr_linenumber" name="71" href="#71">71</a>  <em class="jxr_javadoccomment"> * source document transformation respectively.</em>
<a class="jxr_linenumber" name="72" href="#72">72</a>  <em class="jxr_javadoccomment"> * &lt;/p&gt;</em>
<a class="jxr_linenumber" name="73" href="#73">73</a>  <em class="jxr_javadoccomment"> * </em>
<a class="jxr_linenumber" name="74" href="#74">74</a>  <em class="jxr_javadoccomment"> * @author davewingate</em>
<a class="jxr_linenumber" name="75" href="#75">75</a>  <em class="jxr_javadoccomment"> * </em>
<a class="jxr_linenumber" name="76" href="#76">76</a>  <em class="jxr_javadoccomment"> */</em>
<a class="jxr_linenumber" name="77" href="#77">77</a>  <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">class</strong> <a href="../../../../../net/big_oh/common/algorithms/winnowing/WinnowingFingerprinter.html">WinnowingFingerprinter</a>
<a class="jxr_linenumber" name="78" href="#78">78</a>  {
<a class="jxr_linenumber" name="79" href="#79">79</a>  
<a class="jxr_linenumber" name="80" href="#80">80</a>  	<strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">final</strong> List&lt;WinnowingWhitespaceFilter&gt; whitespaceFilters;
<a class="jxr_linenumber" name="81" href="#81">81</a>  	<strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">final</strong> List&lt;WinnowingTextTransformer&gt; transformers;
<a class="jxr_linenumber" name="82" href="#82">82</a>  	<strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">int</strong> k;
<a class="jxr_linenumber" name="83" href="#83">83</a>  	<strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">int</strong> t;
<a class="jxr_linenumber" name="84" href="#84">84</a>  	<strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">final</strong> String hashingAlgorithm;
<a class="jxr_linenumber" name="85" href="#85">85</a>  
<a class="jxr_linenumber" name="86" href="#86">86</a>  	<em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="87" href="#87">87</a>  <em class="jxr_javadoccomment">	 * </em>
<a class="jxr_linenumber" name="88" href="#88">88</a>  <em class="jxr_javadoccomment">	 * A default constructor that uses MD5 as the hashing algorithm and performs</em>
<a class="jxr_linenumber" name="89" href="#89">89</a>  <em class="jxr_javadoccomment">	 * no preprocessing on source documents before fingerprinting.</em>
<a class="jxr_linenumber" name="90" href="#90">90</a>  <em class="jxr_javadoccomment">	 * </em>
<a class="jxr_linenumber" name="91" href="#91">91</a>  <em class="jxr_javadoccomment">	 * @param k</em>
<a class="jxr_linenumber" name="92" href="#92">92</a>  <em class="jxr_javadoccomment">	 *            The size of the document k-grams that will be fingerprinted.</em>
<a class="jxr_linenumber" name="93" href="#93">93</a>  <em class="jxr_javadoccomment">	 *            Set k to the largest size that will not preclude the detection</em>
<a class="jxr_linenumber" name="94" href="#94">94</a>  <em class="jxr_javadoccomment">	 *            of "interesting" duplicates.</em>
<a class="jxr_linenumber" name="95" href="#95">95</a>  <em class="jxr_javadoccomment">	 * @param t</em>
<a class="jxr_linenumber" name="96" href="#96">96</a>  <em class="jxr_javadoccomment">	 *            The guarantee threshold. Duplicates of length t or greater are</em>
<a class="jxr_linenumber" name="97" href="#97">97</a>  <em class="jxr_javadoccomment">	 *            guaranteed to be detectable using the resulting document</em>
<a class="jxr_linenumber" name="98" href="#98">98</a>  <em class="jxr_javadoccomment">	 *            fingerprints.</em>
<a class="jxr_linenumber" name="99" href="#99">99</a>  <em class="jxr_javadoccomment">	 * @throws IllegalArgumentException</em>
<a class="jxr_linenumber" name="100" href="#100">100</a> <em class="jxr_javadoccomment">	 *             Thrown when the values for k or t are illegal. The value for</em>
<a class="jxr_linenumber" name="101" href="#101">101</a> <em class="jxr_javadoccomment">	 *             k must be greater than zero. The value for t canto be less</em>
<a class="jxr_linenumber" name="102" href="#102">102</a> <em class="jxr_javadoccomment">	 *             than k.</em>
<a class="jxr_linenumber" name="103" href="#103">103</a> <em class="jxr_javadoccomment">	 */</em>
<a class="jxr_linenumber" name="104" href="#104">104</a> 	<strong class="jxr_keyword">public</strong> <a href="../../../../../net/big_oh/common/algorithms/winnowing/WinnowingFingerprinter.html">WinnowingFingerprinter</a>(<strong class="jxr_keyword">int</strong> k, <strong class="jxr_keyword">int</strong> t) <strong class="jxr_keyword">throws</strong> IllegalArgumentException
<a class="jxr_linenumber" name="105" href="#105">105</a> 	{
<a class="jxr_linenumber" name="106" href="#106">106</a> 		<strong class="jxr_keyword">this</strong>(<strong class="jxr_keyword">new</strong> ArrayList&lt;WinnowingWhitespaceFilter&gt;(0), <strong class="jxr_keyword">new</strong> ArrayList&lt;WinnowingTextTransformer&gt;(0), k, t, <span class="jxr_string">"MD5"</span>);
<a class="jxr_linenumber" name="107" href="#107">107</a> 	}
<a class="jxr_linenumber" name="108" href="#108">108</a> 
<a class="jxr_linenumber" name="109" href="#109">109</a> 	<em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="110" href="#110">110</a> <em class="jxr_javadoccomment">	 * </em>
<a class="jxr_linenumber" name="111" href="#111">111</a> <em class="jxr_javadoccomment">	 * @param whitespaceFilters</em>
<a class="jxr_linenumber" name="112" href="#112">112</a> <em class="jxr_javadoccomment">	 *            The list of filters that will be used to remove whitespace</em>
<a class="jxr_linenumber" name="113" href="#113">113</a> <em class="jxr_javadoccomment">	 *            from documents before they are fingerprinted. The definition</em>
<a class="jxr_linenumber" name="114" href="#114">114</a> <em class="jxr_javadoccomment">	 *            of "whitespace" will vary across domains.</em>
<a class="jxr_linenumber" name="115" href="#115">115</a> <em class="jxr_javadoccomment">	 * @param transformers</em>
<a class="jxr_linenumber" name="116" href="#116">116</a> <em class="jxr_javadoccomment">	 *            The list of transformers that are used to translate source</em>
<a class="jxr_linenumber" name="117" href="#117">117</a> <em class="jxr_javadoccomment">	 *            documents to a canonical form prior to fingerprinting.</em>
<a class="jxr_linenumber" name="118" href="#118">118</a> <em class="jxr_javadoccomment">	 * @param k</em>
<a class="jxr_linenumber" name="119" href="#119">119</a> <em class="jxr_javadoccomment">	 *            The size of the document k-grams that will be fingerprinted.</em>
<a class="jxr_linenumber" name="120" href="#120">120</a> <em class="jxr_javadoccomment">	 *            Set k to the largest size that will not preclude the detection</em>
<a class="jxr_linenumber" name="121" href="#121">121</a> <em class="jxr_javadoccomment">	 *            of "interesting" duplicates.</em>
<a class="jxr_linenumber" name="122" href="#122">122</a> <em class="jxr_javadoccomment">	 * @param t</em>
<a class="jxr_linenumber" name="123" href="#123">123</a> <em class="jxr_javadoccomment">	 *            The guarantee threshold. Duplicates of length t or greater are</em>
<a class="jxr_linenumber" name="124" href="#124">124</a> <em class="jxr_javadoccomment">	 *            guaranteed to be detectable using the resulting document</em>
<a class="jxr_linenumber" name="125" href="#125">125</a> <em class="jxr_javadoccomment">	 *            fingerprints.</em>
<a class="jxr_linenumber" name="126" href="#126">126</a> <em class="jxr_javadoccomment">	 * @param hashingAlgorithm</em>
<a class="jxr_linenumber" name="127" href="#127">127</a> <em class="jxr_javadoccomment">	 *            You might use MD5 or SHA1. In any case, select a hashing</em>
<a class="jxr_linenumber" name="128" href="#128">128</a> <em class="jxr_javadoccomment">	 *            algorithm that makes accidental fingerprint collisions</em>
<a class="jxr_linenumber" name="129" href="#129">129</a> <em class="jxr_javadoccomment">	 *            extremely unlikely.</em>
<a class="jxr_linenumber" name="130" href="#130">130</a> <em class="jxr_javadoccomment">	 * @throws IllegalArgumentException</em>
<a class="jxr_linenumber" name="131" href="#131">131</a> <em class="jxr_javadoccomment">	 *             Thrown when the values for k or t are illegal. The value for</em>
<a class="jxr_linenumber" name="132" href="#132">132</a> <em class="jxr_javadoccomment">	 *             k must be greater than zero. The value for t canto be less</em>
<a class="jxr_linenumber" name="133" href="#133">133</a> <em class="jxr_javadoccomment">	 *             than k.</em>
<a class="jxr_linenumber" name="134" href="#134">134</a> <em class="jxr_javadoccomment">	 */</em>
<a class="jxr_linenumber" name="135" href="#135">135</a> 	<strong class="jxr_keyword">public</strong> <a href="../../../../../net/big_oh/common/algorithms/winnowing/WinnowingFingerprinter.html">WinnowingFingerprinter</a>(List&lt;WinnowingWhitespaceFilter&gt; whitespaceFilters, List&lt;WinnowingTextTransformer&gt; transformers, <strong class="jxr_keyword">int</strong> k, <strong class="jxr_keyword">int</strong> t, String hashingAlgorithm) <strong class="jxr_keyword">throws</strong> IllegalArgumentException
<a class="jxr_linenumber" name="136" href="#136">136</a> 	{
<a class="jxr_linenumber" name="137" href="#137">137</a> 		<strong class="jxr_keyword">super</strong>();
<a class="jxr_linenumber" name="138" href="#138">138</a> 		<strong class="jxr_keyword">this</strong>.whitespaceFilters = Collections.unmodifiableList(whitespaceFilters);
<a class="jxr_linenumber" name="139" href="#139">139</a> 		<strong class="jxr_keyword">this</strong>.transformers = Collections.unmodifiableList(transformers);
<a class="jxr_linenumber" name="140" href="#140">140</a> 		<strong class="jxr_keyword">this</strong>.k = k;
<a class="jxr_linenumber" name="141" href="#141">141</a> 		<strong class="jxr_keyword">this</strong>.t = t;
<a class="jxr_linenumber" name="142" href="#142">142</a> 		<strong class="jxr_keyword">this</strong>.hashingAlgorithm = hashingAlgorithm;
<a class="jxr_linenumber" name="143" href="#143">143</a> 
<a class="jxr_linenumber" name="144" href="#144">144</a> 		<strong class="jxr_keyword">if</strong> (k &lt; 1)
<a class="jxr_linenumber" name="145" href="#145">145</a> 		{
<a class="jxr_linenumber" name="146" href="#146">146</a> 			<strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> IllegalArgumentException(<span class="jxr_string">"k cannot be less than one"</span>);
<a class="jxr_linenumber" name="147" href="#147">147</a> 		}
<a class="jxr_linenumber" name="148" href="#148">148</a> 
<a class="jxr_linenumber" name="149" href="#149">149</a> 		<strong class="jxr_keyword">if</strong> (t &lt; k)
<a class="jxr_linenumber" name="150" href="#150">150</a> 		{
<a class="jxr_linenumber" name="151" href="#151">151</a> 			<strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> IllegalArgumentException(<span class="jxr_string">"t cannot be less than k"</span>);
<a class="jxr_linenumber" name="152" href="#152">152</a> 		}
<a class="jxr_linenumber" name="153" href="#153">153</a> 
<a class="jxr_linenumber" name="154" href="#154">154</a> 	}
<a class="jxr_linenumber" name="155" href="#155">155</a> 
<a class="jxr_linenumber" name="156" href="#156">156</a> 	<em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="157" href="#157">157</a> <em class="jxr_javadoccomment">	 * </em>
<a class="jxr_linenumber" name="158" href="#158">158</a> <em class="jxr_javadoccomment">	 * @param sourceDocument</em>
<a class="jxr_linenumber" name="159" href="#159">159</a> <em class="jxr_javadoccomment">	 * @return A set of BigInteger values that are the hashed k-grams selected</em>
<a class="jxr_linenumber" name="160" href="#160">160</a> <em class="jxr_javadoccomment">	 *         by the algorithm to be the source document's fingerprints.</em>
<a class="jxr_linenumber" name="161" href="#161">161</a> <em class="jxr_javadoccomment">	 * @throws NoSuchAlgorithmException</em>
<a class="jxr_linenumber" name="162" href="#162">162</a> <em class="jxr_javadoccomment">	 */</em>
<a class="jxr_linenumber" name="163" href="#163">163</a> 	<strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">final</strong> Set&lt;BigInteger&gt; fingerprint(String sourceDocument) <strong class="jxr_keyword">throws</strong> NoSuchAlgorithmException
<a class="jxr_linenumber" name="164" href="#164">164</a> 	{
<a class="jxr_linenumber" name="165" href="#165">165</a> 
<a class="jxr_linenumber" name="166" href="#166">166</a> 		<em class="jxr_comment">// Copy the string reference, don't want to lose the original input</em>
<a class="jxr_linenumber" name="167" href="#167">167</a> 		String toFingerPrint = sourceDocument;
<a class="jxr_linenumber" name="168" href="#168">168</a> 
<a class="jxr_linenumber" name="169" href="#169">169</a> 		<em class="jxr_comment">// perform transformations</em>
<a class="jxr_linenumber" name="170" href="#170">170</a> 		<strong class="jxr_keyword">for</strong> (WinnowingTextTransformer transformer : transformers)
<a class="jxr_linenumber" name="171" href="#171">171</a> 		{
<a class="jxr_linenumber" name="172" href="#172">172</a> 			toFingerPrint = transformer.doTransformation(toFingerPrint);
<a class="jxr_linenumber" name="173" href="#173">173</a> 		}
<a class="jxr_linenumber" name="174" href="#174">174</a> 
<a class="jxr_linenumber" name="175" href="#175">175</a> 		<em class="jxr_comment">// remove whitespace</em>
<a class="jxr_linenumber" name="176" href="#176">176</a> 		<strong class="jxr_keyword">for</strong> (WinnowingWhitespaceFilter filter : whitespaceFilters)
<a class="jxr_linenumber" name="177" href="#177">177</a> 		{
<a class="jxr_linenumber" name="178" href="#178">178</a> 			toFingerPrint = filter.doFilter(toFingerPrint);
<a class="jxr_linenumber" name="179" href="#179">179</a> 		}
<a class="jxr_linenumber" name="180" href="#180">180</a> 
<a class="jxr_linenumber" name="181" href="#181">181</a> 		<em class="jxr_comment">// handle the exceptional case in which the filtered/transformed</em>
<a class="jxr_linenumber" name="182" href="#182">182</a> 		<em class="jxr_comment">// originalInput is shorter than the value set for k</em>
<a class="jxr_linenumber" name="183" href="#183">183</a> 		<strong class="jxr_keyword">if</strong> (toFingerPrint.length() &lt; k)
<a class="jxr_linenumber" name="184" href="#184">184</a> 		{
<a class="jxr_linenumber" name="185" href="#185">185</a> 			<strong class="jxr_keyword">return</strong> Collections.emptySet();
<a class="jxr_linenumber" name="186" href="#186">186</a> 		}
<a class="jxr_linenumber" name="187" href="#187">187</a> 
<a class="jxr_linenumber" name="188" href="#188">188</a> 		<em class="jxr_comment">// generate k-grams</em>
<a class="jxr_linenumber" name="189" href="#189">189</a> 		List&lt;String&gt; orderedKGrams = generateKGrams(toFingerPrint);
<a class="jxr_linenumber" name="190" href="#190">190</a> 
<a class="jxr_linenumber" name="191" href="#191">191</a> 		<em class="jxr_comment">// hash kGrams</em>
<a class="jxr_linenumber" name="192" href="#192">192</a> 		List&lt;BigInteger&gt; hashedOrderedKGrams = <strong class="jxr_keyword">new</strong> ArrayList&lt;BigInteger&gt;(orderedKGrams.size());
<a class="jxr_linenumber" name="193" href="#193">193</a> 		<strong class="jxr_keyword">for</strong> (String kg : orderedKGrams)
<a class="jxr_linenumber" name="194" href="#194">194</a> 		{
<a class="jxr_linenumber" name="195" href="#195">195</a> 			hashedOrderedKGrams.add(hashKGram(kg));
<a class="jxr_linenumber" name="196" href="#196">196</a> 		}
<a class="jxr_linenumber" name="197" href="#197">197</a> 
<a class="jxr_linenumber" name="198" href="#198">198</a> 		<em class="jxr_comment">// calculate window size</em>
<a class="jxr_linenumber" name="199" href="#199">199</a> 		<strong class="jxr_keyword">int</strong> w = t - k + 1;
<a class="jxr_linenumber" name="200" href="#200">200</a> 
<a class="jxr_linenumber" name="201" href="#201">201</a> 		<em class="jxr_comment">// prepare to select fingerprint hashes</em>
<a class="jxr_linenumber" name="202" href="#202">202</a> 		Set&lt;BigInteger&gt; fingerprintHashes = <strong class="jxr_keyword">new</strong> HashSet&lt;BigInteger&gt;();
<a class="jxr_linenumber" name="203" href="#203">203</a> 
<a class="jxr_linenumber" name="204" href="#204">204</a> 		<em class="jxr_comment">// handle the exceptional case in which the window size is greater than</em>
<a class="jxr_linenumber" name="205" href="#205">205</a> 		<em class="jxr_comment">// the number of hashedOrderedKGrams</em>
<a class="jxr_linenumber" name="206" href="#206">206</a> 		<strong class="jxr_keyword">if</strong> (w &gt; hashedOrderedKGrams.size())
<a class="jxr_linenumber" name="207" href="#207">207</a> 		{
<a class="jxr_linenumber" name="208" href="#208">208</a> 
<a class="jxr_linenumber" name="209" href="#209">209</a> 			fingerprintHashes.add(selectMin(hashedOrderedKGrams));
<a class="jxr_linenumber" name="210" href="#210">210</a> 
<a class="jxr_linenumber" name="211" href="#211">211</a> 		}
<a class="jxr_linenumber" name="212" href="#212">212</a> 		<strong class="jxr_keyword">else</strong>
<a class="jxr_linenumber" name="213" href="#213">213</a> 		{
<a class="jxr_linenumber" name="214" href="#214">214</a> 
<a class="jxr_linenumber" name="215" href="#215">215</a> 			<em class="jxr_comment">// select fingerprint hashes by sliding a window of size w across</em>
<a class="jxr_linenumber" name="216" href="#216">216</a> 			<em class="jxr_comment">// hashedOrderedKGrams.</em>
<a class="jxr_linenumber" name="217" href="#217">217</a> 			<strong class="jxr_keyword">for</strong> (<strong class="jxr_keyword">int</strong> windowStartOffset = 0; windowStartOffset + w &lt;= hashedOrderedKGrams.size(); windowStartOffset++)
<a class="jxr_linenumber" name="218" href="#218">218</a> 			{
<a class="jxr_linenumber" name="219" href="#219">219</a> 				fingerprintHashes.add(selectMin(hashedOrderedKGrams.subList(windowStartOffset, windowStartOffset + w)));
<a class="jxr_linenumber" name="220" href="#220">220</a> 			}
<a class="jxr_linenumber" name="221" href="#221">221</a> 
<a class="jxr_linenumber" name="222" href="#222">222</a> 		}
<a class="jxr_linenumber" name="223" href="#223">223</a> 
<a class="jxr_linenumber" name="224" href="#224">224</a> 		<strong class="jxr_keyword">return</strong> fingerprintHashes;
<a class="jxr_linenumber" name="225" href="#225">225</a> 
<a class="jxr_linenumber" name="226" href="#226">226</a> 	}
<a class="jxr_linenumber" name="227" href="#227">227</a> 
<a class="jxr_linenumber" name="228" href="#228">228</a> 	<strong class="jxr_keyword">final</strong> BigInteger selectMin(List&lt;BigInteger&gt; integers)
<a class="jxr_linenumber" name="229" href="#229">229</a> 	{
<a class="jxr_linenumber" name="230" href="#230">230</a> 		<strong class="jxr_keyword">if</strong> (integers.isEmpty())
<a class="jxr_linenumber" name="231" href="#231">231</a> 		{
<a class="jxr_linenumber" name="232" href="#232">232</a> 			<strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> RuntimeException(<span class="jxr_string">"unexpected"</span>);
<a class="jxr_linenumber" name="233" href="#233">233</a> 		}
<a class="jxr_linenumber" name="234" href="#234">234</a> 
<a class="jxr_linenumber" name="235" href="#235">235</a> 		BigInteger min = integers.get(0);
<a class="jxr_linenumber" name="236" href="#236">236</a> 
<a class="jxr_linenumber" name="237" href="#237">237</a> 		<strong class="jxr_keyword">for</strong> (BigInteger candidate : integers)
<a class="jxr_linenumber" name="238" href="#238">238</a> 		{
<a class="jxr_linenumber" name="239" href="#239">239</a> 			<strong class="jxr_keyword">if</strong> (candidate.compareTo(min) &lt; 0)
<a class="jxr_linenumber" name="240" href="#240">240</a> 			{
<a class="jxr_linenumber" name="241" href="#241">241</a> 				min = candidate;
<a class="jxr_linenumber" name="242" href="#242">242</a> 			}
<a class="jxr_linenumber" name="243" href="#243">243</a> 		}
<a class="jxr_linenumber" name="244" href="#244">244</a> 
<a class="jxr_linenumber" name="245" href="#245">245</a> 		<strong class="jxr_keyword">return</strong> min;
<a class="jxr_linenumber" name="246" href="#246">246</a> 
<a class="jxr_linenumber" name="247" href="#247">247</a> 	}
<a class="jxr_linenumber" name="248" href="#248">248</a> 
<a class="jxr_linenumber" name="249" href="#249">249</a> 	<strong class="jxr_keyword">final</strong> List&lt;String&gt; generateKGrams(String toFingerPrint)
<a class="jxr_linenumber" name="250" href="#250">250</a> 	{
<a class="jxr_linenumber" name="251" href="#251">251</a> 		List&lt;String&gt; kGrams = <strong class="jxr_keyword">new</strong> ArrayList&lt;String&gt;(toFingerPrint.length());
<a class="jxr_linenumber" name="252" href="#252">252</a> 
<a class="jxr_linenumber" name="253" href="#253">253</a> 		<em class="jxr_comment">// generate kGrams by sliding a window of size k across the characters</em>
<a class="jxr_linenumber" name="254" href="#254">254</a> 		<em class="jxr_comment">// of toFingerPrint</em>
<a class="jxr_linenumber" name="255" href="#255">255</a> 		<strong class="jxr_keyword">for</strong> (<strong class="jxr_keyword">int</strong> windowStartOffset = 0; windowStartOffset + k &lt;= toFingerPrint.length(); windowStartOffset++)
<a class="jxr_linenumber" name="256" href="#256">256</a> 		{
<a class="jxr_linenumber" name="257" href="#257">257</a> 			kGrams.add(toFingerPrint.substring(windowStartOffset, windowStartOffset + k));
<a class="jxr_linenumber" name="258" href="#258">258</a> 		}
<a class="jxr_linenumber" name="259" href="#259">259</a> 
<a class="jxr_linenumber" name="260" href="#260">260</a> 		<strong class="jxr_keyword">return</strong> kGrams;
<a class="jxr_linenumber" name="261" href="#261">261</a> 	}
<a class="jxr_linenumber" name="262" href="#262">262</a> 
<a class="jxr_linenumber" name="263" href="#263">263</a> 	<strong class="jxr_keyword">final</strong> BigInteger hashKGram(String kGram) <strong class="jxr_keyword">throws</strong> NoSuchAlgorithmException
<a class="jxr_linenumber" name="264" href="#264">264</a> 	{
<a class="jxr_linenumber" name="265" href="#265">265</a> 		MessageDigest md = MessageDigest.getInstance(hashingAlgorithm);
<a class="jxr_linenumber" name="266" href="#266">266</a> 		byte[] digestedKGram = md.digest(kGram.getBytes());
<a class="jxr_linenumber" name="267" href="#267">267</a> 		<strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">new</strong> BigInteger(1, digestedKGram);
<a class="jxr_linenumber" name="268" href="#268">268</a> 	}
<a class="jxr_linenumber" name="269" href="#269">269</a> 
<a class="jxr_linenumber" name="270" href="#270">270</a> 	<em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="271" href="#271">271</a> <em class="jxr_javadoccomment">	 * </em>
<a class="jxr_linenumber" name="272" href="#272">272</a> <em class="jxr_javadoccomment">	 * @return The size of the document k-grams that will be fingerprinted. Set</em>
<a class="jxr_linenumber" name="273" href="#273">273</a> <em class="jxr_javadoccomment">	 *         k to the largest size that will not preclude the detection of</em>
<a class="jxr_linenumber" name="274" href="#274">274</a> <em class="jxr_javadoccomment">	 *         "interesting" duplicates.</em>
<a class="jxr_linenumber" name="275" href="#275">275</a> <em class="jxr_javadoccomment">	 */</em>
<a class="jxr_linenumber" name="276" href="#276">276</a> 	<strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">int</strong> getK()
<a class="jxr_linenumber" name="277" href="#277">277</a> 	{
<a class="jxr_linenumber" name="278" href="#278">278</a> 		<strong class="jxr_keyword">return</strong> k;
<a class="jxr_linenumber" name="279" href="#279">279</a> 	}
<a class="jxr_linenumber" name="280" href="#280">280</a> 
<a class="jxr_linenumber" name="281" href="#281">281</a> 	<em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="282" href="#282">282</a> <em class="jxr_javadoccomment">	 * </em>
<a class="jxr_linenumber" name="283" href="#283">283</a> <em class="jxr_javadoccomment">	 * @return The guarantee threshold. Duplicates of length t or greater are</em>
<a class="jxr_linenumber" name="284" href="#284">284</a> <em class="jxr_javadoccomment">	 *         guaranteed to be detectable using the resulting document</em>
<a class="jxr_linenumber" name="285" href="#285">285</a> <em class="jxr_javadoccomment">	 *         fingerprints.</em>
<a class="jxr_linenumber" name="286" href="#286">286</a> <em class="jxr_javadoccomment">	 */</em>
<a class="jxr_linenumber" name="287" href="#287">287</a> 	<strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">int</strong> getT()
<a class="jxr_linenumber" name="288" href="#288">288</a> 	{
<a class="jxr_linenumber" name="289" href="#289">289</a> 		<strong class="jxr_keyword">return</strong> t;
<a class="jxr_linenumber" name="290" href="#290">290</a> 	}
<a class="jxr_linenumber" name="291" href="#291">291</a> 
<a class="jxr_linenumber" name="292" href="#292">292</a> 	<em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="293" href="#293">293</a> <em class="jxr_javadoccomment">	 * </em>
<a class="jxr_linenumber" name="294" href="#294">294</a> <em class="jxr_javadoccomment">	 * @return The hashing algorithm used to generate fingerprints for a source</em>
<a class="jxr_linenumber" name="295" href="#295">295</a> <em class="jxr_javadoccomment">	 *         document's k-grams.</em>
<a class="jxr_linenumber" name="296" href="#296">296</a> <em class="jxr_javadoccomment">	 */</em>
<a class="jxr_linenumber" name="297" href="#297">297</a> 	<strong class="jxr_keyword">public</strong> String getHashingAlgorithm()
<a class="jxr_linenumber" name="298" href="#298">298</a> 	{
<a class="jxr_linenumber" name="299" href="#299">299</a> 		<strong class="jxr_keyword">return</strong> hashingAlgorithm;
<a class="jxr_linenumber" name="300" href="#300">300</a> 	}
<a class="jxr_linenumber" name="301" href="#301">301</a> 
<a class="jxr_linenumber" name="302" href="#302">302</a> 	<em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="303" href="#303">303</a> <em class="jxr_javadoccomment">	 * </em>
<a class="jxr_linenumber" name="304" href="#304">304</a> <em class="jxr_javadoccomment">	 * @return The list of filters that will be used to remove whitespace from</em>
<a class="jxr_linenumber" name="305" href="#305">305</a> <em class="jxr_javadoccomment">	 *         documents before they are fingerprinted. The definition of</em>
<a class="jxr_linenumber" name="306" href="#306">306</a> <em class="jxr_javadoccomment">	 *         "whitespace" will vary across domains.</em>
<a class="jxr_linenumber" name="307" href="#307">307</a> <em class="jxr_javadoccomment">	 */</em>
<a class="jxr_linenumber" name="308" href="#308">308</a> 	<strong class="jxr_keyword">public</strong> List&lt;WinnowingWhitespaceFilter&gt; getWhitespaceFilters()
<a class="jxr_linenumber" name="309" href="#309">309</a> 	{
<a class="jxr_linenumber" name="310" href="#310">310</a> 		<strong class="jxr_keyword">return</strong> whitespaceFilters;
<a class="jxr_linenumber" name="311" href="#311">311</a> 	}
<a class="jxr_linenumber" name="312" href="#312">312</a> 
<a class="jxr_linenumber" name="313" href="#313">313</a> 	<em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="314" href="#314">314</a> <em class="jxr_javadoccomment">	 * </em>
<a class="jxr_linenumber" name="315" href="#315">315</a> <em class="jxr_javadoccomment">	 * @return The list of transformers that are used to translate source</em>
<a class="jxr_linenumber" name="316" href="#316">316</a> <em class="jxr_javadoccomment">	 *         documents to a canonical form prior to fingerprinting.</em>
<a class="jxr_linenumber" name="317" href="#317">317</a> <em class="jxr_javadoccomment">	 */</em>
<a class="jxr_linenumber" name="318" href="#318">318</a> 	<strong class="jxr_keyword">public</strong> List&lt;WinnowingTextTransformer&gt; getTransformers()
<a class="jxr_linenumber" name="319" href="#319">319</a> 	{
<a class="jxr_linenumber" name="320" href="#320">320</a> 		<strong class="jxr_keyword">return</strong> transformers;
<a class="jxr_linenumber" name="321" href="#321">321</a> 	}
<a class="jxr_linenumber" name="322" href="#322">322</a> 
<a class="jxr_linenumber" name="323" href="#323">323</a> }
</pre>
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